Create SQL data source utils class

- Extract logic used in SQLite and MySQL for logging and closing SQL objects
    - Decided to leave buildAuthFromResultSet methods individually as this might be more implementation-specific
- Rename DataSource#close to DataSource#closeConnection to fix conflict with static import

src/main/java/fr/xephi/authme/datasource/SqlDataSourceUtils.java

@@ -0,0 +1,75 @@
+package fr.xephi.authme.datasource;
+
+import fr.xephi.authme.ConsoleLogger;
+
+import java.sql.Connection;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+
+/**
+ * Utilities for SQL data sources.
+ */
+final class SqlDataSourceUtils {
+
+    private SqlDataSourceUtils() {
+    }
+
+    /**
+     * Logs a SQL exception.
+     *
+     * @param e the exception to log
+     */
+    static void logSqlException(SQLException e) {
+        ConsoleLogger.logException("Error during SQL operation:", e);
+    }
+
+
+    // We use overloaded close() methods instead of one close(AutoCloseable) method in order to limit the
+    // checked exceptions to SQLException, which is the only checked exception these classes throw.
+
+    /**
+     * Closes a {@link ResultSet} safely.
+     *
+     * @param rs the result set to close
+     */
+    static void close(ResultSet rs) {
+        try {
+            if (rs != null && !rs.isClosed()) {
+                rs.close();
+            }
+        } catch (SQLException e) {
+            ConsoleLogger.logException("Could not close ResultSet", e);
+        }
+    }
+
+    /**
+     * Closes a {@link Statement} safely.
+     *
+     * @param st the statement set to close
+     */
+    static void close(Statement st) {
+        try {
+            if (st != null && !st.isClosed()) {
+                st.close();
+            }
+        } catch (SQLException e) {
+            ConsoleLogger.logException("Could not close Statement", e);
+        }
+    }
+
+    /**
+     * Closes a {@link Connection} safely.
+     *
+     * @param con the connection set to close
+     */
+    static void close(Connection con) {
+        try {
+            if (con != null && !con.isClosed()) {
+                con.close();
+            }
+        } catch (SQLException e) {
+            ConsoleLogger.logException("Could not close Connection", e);
+        }
+    }
+}